#include <iostream>

using namespace std;

int main() {
/*
    int year;

    cin >> year;
    if((year%4==0 && year%100!=0) || (year%400==0)) {
        cout << "Yes" << endl;
    } else {
        cout << "No" << endl;
    }
*/

 /*
    鸡: J
    兔: T
    Math:
        J + T = n
        2*J + 4*T = m
    Code:
        J = (4*n - m) / 2
        T = n - J
 */
 /*
    int J, T;
    int n, m;

    cin >> n >> m;
    J = (4*n - m) / 2;
    T = n - J;

    if(m%2==1 || J < 0 || T < 0) {
        cout << "NO answer" << endl;
    } else {
        cout << J << " " << T << endl;
    }
*/

  /*
    int num1, num2, num3;
    int max;   // 专门用来表示这三个数中的最大数

    cin >> num1 >> num2 >> num3;
    max = num1;   // 假设 num1 就是最大的

    if(num2 > max) {
        max = num2;
    }
    if(num3 > max) {
        max = num3;
    }

    cout << max * max << endl;
*/
    // n   x    y
    // m = y / x  --> n - m
    // 10 2 6  -->  6 % 3 == 0
    // 3 = 6 / 2     7 = 10 - 3

    // 10 2 7   7 % 2 != 0
    // 3 = 7 / 2      3 + 1
    // 6 = 10 - 4

    int n, x, y;
    int m;   // y小时内，吃掉的完整苹果数目

    cin >> n >> x >> y;
    if(y % x == 0) {
        m = y / x;
        n = n - m;
    }
    if(y % x != 0) {
        m = y / x;
        m = m + 1;
        n = n - m;
    }

    if(n < 0) {
        cout << "0" << endl;
    } else {
        cout << n << endl;
    }


    return 0;
}
